Nucleosides and Nucleotides. 175. Structural Requirements of the Sugar Moiety for the Antitumor Activities of New Nucleoside Antimetabolites, 1-(3-<i>C</i>-Ethynyl-β-<scp>d</scp>-<i>r</i><i>ibo</i>-pentofuranosyl)cytosine and -uracil
1-(3-C-ethynyl-beta-d-ribo-pentofuranosyl)uracil (EUrd) and its cytosine congener (ECyd) as potential multifunctional antitumor nucleoside antimetabolites. They showed potent and broad-spectrum antitumor activity against various human and mouse tumor cells in vitro and in vivo. To clarify the structure-activity relationship of the sugarmoiety, various 3'-C-carbon-substituted analogues, such as 1-propynyl